Firebase Auth errorFirebase Auth: auth/invalid-user-token

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Why Firebase rejects the user, and the fix

1. 01

   The app moved to another Firebase project

   “The user must sign in again.” Firebase, firebase.auth.Error (auth/invalid-user-token)

   The browser or device still holds a user from the old project, and the new config can’t use it. Sign out on the first error so the user signs in to the current project.

   import { getAuth, signOut } from 'firebase/auth';
   
   const auth = getAuth();
   try {
     await auth.currentUser?.getIdToken(true);
   } catch (error) {
     if (error.code === 'auth/invalid-user-token') {
       await signOut(auth);
       showSignIn();
     }
   }

2. 02

   Emulator and production users are mixed

   A user created against the Auth emulator is not valid for the production project. Use a separate origin or storage for emulator builds, or sign out when switching.

3. 03

   The token was changed in storage

   Edited or copied auth data in IndexedDB or local storage is rejected. Don’t write to Firebase’s persisted auth state; sign in again to get a fresh token.

4. 04

   The app treats it like an expired token

   Also check: unlike auth/user-token-expired, the SDK does not sign the user out for this code. Handle it in the app, or the stale user stays in currentUser.

Checked against the vendor’s docs on November 9, 2026: Firebase reference: firebase.auth.Error; Firebase JS SDK source: auth errors; Firebase JS SDK source: server error mapping.

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Related: Firebase auth/user-token-expired · Firebase auth/invalid-api-key in production · Firebase auth/user-disabled · Firebase missing-or-invalid-nonce